It has been shown by several labs including our own, that development of cells involves differential activity of certain protein tyrosine kinases. In order to study this further we are attempting to clone genes encoding tyrosine kinases from a cDNA library using immunological probes. Once the clones are isolated it will be necessary to identify them through sequence analysis. The sequences will then be compared to known sequences using existing libraries such as Genbank, etc. Using the sequence information thus acquired along with biochemical data about the activity of the proteins in cells in various states of differentiation, it should be possible to make some conclusions about the role (s) of the isolated gene products during development.